"Last October I blogged about our plan to release the source code to the .NET Framework libraries, and enable debugging support of them with Visual Studio 2008. Today I'm happy to announce that this is now available for everyone to use. Specifically, you can now browse and debug the source code for the following .NET Framework libraries."

The GNU General Public License allows you to:
* read the source code
* modify the source code
* include portions of the source code in other software
* redistribute the original source code
* distribute modified copies of the source code

The GPL may impose some restrictions, but comparing it to the MS-RL is just ridiculous.